"Breeding-back" aims to restore or immitate extinct animals by selective breeding. This blog provides general information, the facts behind myths and news from various projects.

Thursday, 15 January 2015

Dedomestication series Pt.III: In which way feral cattle might evolve

Immunological
adaptions would not be visible. Adaptions to climate would show in the
structure of the fur – cold winters, no matter if dry or wet, require dense fur
that isolates the animal to reduce heat loss. The overgrown long hair of
Highland cattle, on the other hand, is known to be disadvantageous even in
Central European summers, not to speak of Southern European summers. Usually,
cattle winter fur is bilayered.

Body
proportions and conformation probably would change dramatically. We know that
the proportions and the body shape of domestic cattle are very different from
the aurochs and other wild cattle. The trunk of cattle got longer and limbs and
head shorter. This is not merely an aesthetic flaw but also a functional,
because there is a reason why wild cattle have the proportions they have. The
shorter the trunk and the longer the legs, the more manoeuvrable is the body.
No need to say that longer limbs enable a higher running pace than shorter
limbs. The trunk of domestic cattle in general is heavy and the “hump” is
usually very reduced, so the centre of gravity is probably somewhere in the
middle of the trunk or even a little bit posterior. In any (quadrupedal)
mammal, the forelimbs are most important for changes in direction during
running, so a more anterior centre of gravity makes the animal more agile. The
so-called “hump” (actually we are talking about a shoulder area with high
processi spinosi that attach well-developed dorsal and neck muscles) is also,
or even more so, advantageous for intra- and interspecific fight. That’s
exactly the function of this trait, and all wild bovines – including the
aurochs – have it. Stronger back- and neck muscles are a direct advantage when
pulling the opponent away, pushing or stabbing a conspecific or a predator.

Without
question, cattle with those morphological traits should have a way higher
evolutionary fitness than those who are proportionated and shaped like domestic
cattle.

The size,
shape and orientation of the horns likely also has a direct influence on evolutionary
fitness. Horns and antlers evolved as a tool for intraspecific competition for
dominance and breeding rights. In my view, the shape of the horns in cattle has
a primarily mechanic function. Cattle fight by pulling and pushing the opponent
in a head-to-head and horn-to-horn fight. Not only bulls but also cows fight this way. It is clear that horns need to have a certain shape and size for
that. It is most advantageous when the horns curve outwards at first and then
inwards and a little bit upwards, instead of being curled outwards or pointing
directly outwards. Also it is probably advantageous when they do not have an
either very high or very low orientation relative to the skull. And it might
also make sense that larger horns are more useful than smaller horns in such a
competition until a certain size. So it seems logical that intraspecific fights
would affect horn shape, orientation and size. Other large bovines that do not
have the same kind of horns also have different fighting modes, take bison for
example. Horns are of course defensive weapons as well, but selection by
predation probably tolerates more kinds of horn shapes than intraspecific
competition does.

Large body
size is favoured by predation and intraspecific fights. The larger and stronger
the animal, the better the chances of succeeding.

Physical
competition would likely require behavioural changes as well, as outlined
above. Natural selection would definitely favour the alleles responsible for an
energetic temper and the will to take risks. This might cause a kind of
reversal of the hormonal, and therefore developmental, changes that took place
during domestication. Perhaps the level of corticosteroids, responsible for the
fight/flight reaction, and thyroid hormones (low levels of these cause shorter
limbs and snouts, floppy ears and reduced body size in laboratory rats), would
rise – the opposite apparently happens during domestication by selection for
tameness (see Pt. I). Maybe it is not a coincidence that Lidia, bred for
aggression, is one of the very few breeds that retained a very aurochs-like
body conformation with a well-pronounced hump, tight muscles and an athletic
posture. However, Lidia are small, but humans actively select them for that.
Regardless of whether the Lidia example is correct, I consider it likely that
natural selection for genes that regulate both behavioural traits and
developmental traits might reduce or eradicate paedomorphism and other
developmental changes that occurred during domestication.

Sexual
selection certainly would increase sexual dimorphism, which had been drastically
reduced during cattle domestication. Bulls with high levels of testosterone are
more likely to win combats, and the larger the bull the higher the chance to
win. The coat colour in wild-type coloured cattle is influenced by testosterone
level: the higher, the stronger the melanisation of the fur, and therefore the
darker the colour. Therefore sexual selection would probably favour larger, stronger
and more hot-tempered bulls with a darker colour. Cows do fight as well, but
these combats cannot be nowhere nearly as important for reproductive success as those of bulls in my
opinion.

Large,
black bulls might also be more attractive to cows than smaller, less melanised
ones. And yes, cows do have a choice to a certain degree – in all harem-systems
there are the so-called “sneakers” that cover cows in moments unwatched by the
dominant bull, and cows do have a choice which one is allowed to mate with them.

Needless to
say that environment also directly affects how the cattle are going to evolve.
Apart from climatic factors, nutrition and the size of the area are important.
As outlined in the first part of the Dedomestication series, the morphology of
animals is plastic. Quality and quantity of the food supply affect overall body
size and horn size. Theoretically, intraspecific competition would always prefer
larger over smaller individuals, but on a restricted area with limited food
supply it is harder for larger animals to find enough food than for smaller
ones, and an ill-nourished bull might defeat against a smaller but
well-nourished bull. To put it in a nutshell, the so-called island effect would
take place, especially in the absence of predators.

Colouration

Colour
probably has the weakest effect on the evolutionary fitness of large
herbivores. If white spots are indeed correlated with neuronal deficiencies,
then pleiotropy might work against the piebald pattern, but probably only on a
very long-term sight. However, in a reserve with predators, solid-coloured
calves are definitely better camouflaged than piebald ones when hiding in a
shelter. As I wrote in the first post, a lack of melanisation in cattle skin
increases the risk of developing eye lid cancer. Perhaps dilutions
that also de-melanise the skin, f.e. the allele e “red” which causes lightly-coloured mucous membranes and eyelids
are evolutionary disadvantageous. But the influence likely would be small,
because cancer often develops after reaching reproductive age and it is not
immediately fatal. The “black” mutation Edresults in a solid, uniform black coat colour. I do not see much
disadvantages in this colour, except perhaps signal function. The dorsal stripe
as much as the muzzle ring very likely evolved for that purpose (a white mouth
area is actually widespread among bovids, and wild horses have it too). On the
other hand, the frequency and intensity of muzzle rings in banteng and gaur are
very variable too. In fact I have been speculating that “black” might have
evolved in the aurochs already (just as an idea). Apart from that, we should
not forget that female choice has a far weaker effect on reproductive success
for bulls than combats with other males have, so we have to consider a very long
time span if sexual selection would indeed disadvantage “black”.

So “red”
and “black” will probably remain in the population for a pretty long time, and
without predators white spots would probably too.

How about
brindle, and all those dilution factors causing tan, beige and grey colours? I
don’t know. Again, we can only speculate how large the effect of sexual
selection on the reproductive success of bulls would be. If there is, it would
probably be small, and take very long to wheedle them out of the population. I
am talking of centuries or more. One factor might be predators again. Although
the calves probably wouldn’t be affected since these dilutions show their
affect only when growing their adult coats, single individuals with a lighter
colour might be disadvantaged because they stand out for predators. Brindle
probably would be less problematic.

If a cattle
population living in the wild is exposed to predation to a sufficient extent,
piebald patterns probably would disappear first. Perhaps sufficiently strong
predative pressure would also affect greyish, tan or beige individuals. Sexual
selection probably would take a very long time to affect colouration.

Nevertheless,
sooner or later dedomesticated cattle would be more or less homogeneous in colour. But not
necessarily in the most advantageous way, even if all wild-type colour traits
are present in the founding population. I think so because colour seemingly is
the least important trait for fitness in cattle (except for certain colours
under strong predation pressure, as outlined above). Horns, morphology, weather
tolerance, behaviour, immunology, seasonal mating and other traits are simply
more important. And so it might happen that, coincidentally, some wild-type
colour features get lost while some domestic variants become fixated. Genetic
bottlenecks can have the same effect. So it might – note, might – happen that a
dedomesticed cattle population that is otherwise well-adapted to its
environment has a “red” or diluted coat colour instead of a fully wild-type
colour. Also, it might turn out that selective pressure for a strongly marked sexual dichromatism is not that strong at all and both sexes would show a uniform colour.

All in all,
I think that wild, dedomesticated cattle would develop proportions, body shape
and horns resembling the aurochs because they are functionally advantageous. Pleiotropic
effects and developmental cascades would eradicate paedomorphic traits. Size
would not only be dependent on intraspecific competition and predative
pressure, but also on what the resources of the environment allows. Sexual dimorphism would be
increased, by developmental changes as much as sexual selection. Natural
selection would affect colour the least. Pleiotropy might or might not affect
white spots, but predation very likely would. If strong enough, predation might
speed up the homogenization of the coat colour. Sexual selection might play a
role, but much more important is pure coincidence because the other traits
listened before are more effective and genetic bottlenecks might also be
important. In the end, the dedomesticated population would be homogeneously
coloured, but only after a very long time.

The
behaviour would change as well. Their reproductive circle would adapt to the
season.

All in all
I think that “Does evolution take the same road twice?” is a bad question. Animals
evolve according to what abiotic and biotic factors currently require and to
what their possibilities are, and to a certain degree also coincidence. But
traits that were advantageous in the wild type of a species might also be
advantageous in feral domestic members of the same species because it was (mostly)
not a coincidence that the wild type was the way it was. Especially when the
domestic descendants live under the same or very similar conditions as the wild
type did, which is the case in aurochs and domestic cattle. How fast these
phenotypic changes will occur is dependent on how variable the starting population is
(see Fisher’s fundamental theorem). Behavioural and developmental changes, as
much as the transformation of traits like overall morphology would probably
work without “original alleles” (if there are such) having to be present.
Colour, being regulated by only a few loci, are another thing – the wild-type
colour alleles have to be present in the population if you want that the cattle
will show this type of colouration – it won’t evolve from new. I don’t know if
it is necessary, but it would certainly be helpful and quicker if there were
some cattle in the founding population already that have functionally
advantageous (and therefore aurochs-like) horn traits for such a horn shape to
evolve.

The next post will take a look at existing feral populations and see how far they confirm the predictions in this post.

Interesting this 3 articles, thank u! meanwhile I post here a link for the hybrids between the Wisent and regular domestic cattle showing some very interesting primitive characteristics and I had the pleasure to see them alive: https://www.google.pl/search?q=zubron&source=lnms&tbm=isch&sa=X&ei=_Wm6VI2xF4jOaPTGgKgO&ved=0CAgQ_AUoAQ&biw=1366&bih=631#imgdii=LSKrtDEJRvfwaM%3A%3BnW-XGOzU1vsxWM%3BLSKrtDEJRvfwaM%3A&imgrc=LSKrtDEJRvfwaM%253A%3B8e6rQ2eNfqdChM%3Bhttp%253A%252F%252Fimg1.garnek.pl%252Fa.garnek.pl%252F017%252F442%252F17442602_800.0.jpg%252Fzubron-krzyzowka-krowy-z-zubrem.jpg%3Bhttp%253A%252F%252Fwww.garnek.pl%252Fpassat%252F17442602%252Fzubron-krzyzowka-krowy-z-zubrem%3B800%3B600

Hello Daniel,I would give a response to your comment on my blog http://weertnatuur.blogspot.nl/2014/12/maremmana-primitivo-nakomelingen.html, but could not find your email adres. Thats why I place it in this post. After reading it, you can delete it of course.I will tell you, that you were totally right in your comment that it are Marermmana's.In response to your comment, I recently contacted Denis Frissen, administrator of Kempen-Broek and he confirmed that these are indeed 4 of the 15 Maremmanna that Taurus Foundation in november 2014 has imported from Tuscany. He assured that both the cows ánd the bull are 1000% purity. So I have recently modified the post.

I just wanted to let you know this and thanks again. Greetings Geer vanne Forge.

You wrote that sexual selection would likely be much slower than predator-driven selection against piebald individuals. This is not a likely scenario. Selection speed is always a question of selection pressure. In a group of (let's say) 100 individuals living in the wild, perhaps 10 or 20 may be killed by large predators (i.e. wolves), and only possibly half of these as a result og being easily spotted (piebald). With the social structure of cattle, possibly less than 10 or the oxen will sire the next generation of calves. This mean that about 80% of the bulls won't breed, a far, far stronger selective pressure.

Sexual selection is the reason very ornate species often diverge and form new species. Sexual selection is usually a lot faster than the sluggish pace of natural selection.

Thanks for an interesting and very informative blog, keep up the good work!

What you write is comparing the speed of selection through predators and sexual selection in general. What I was saying is that a piebald coat is of greater disadvantage against predation than in sexual selection because piebald calves lying on the ground (see above) are more dangered to be detected than those without spots. While white spots will be only a rather trivial factor in mating choice. But I agree with you that sexual selection is, at least in such a population, is the faster process, as the changes in horn shape and in some cases hump size at OVP have shown.

True. I think you wrote somewhere else that ox colours hardly seem to matter to the cows. This begs the question of why the aurochs had the colour they did in the first place.

Selection is of course only a half the game. As you have pointed out repeatedly in your blog, the degree to which a trait is heritable is quite another thing. Piebaldism, with it's rather straight forward genetic basis would be more easily affected by selection than the (probably) more complex genetics of horns.

About this blog

This blog is on everything related to the so-called “breeding-back” of extinct animals: From the extinct animals themselves, over their often domestic descendants and dedomestication to news and facts about various breeding-back projects, reports and photos from my own breeding-back related trips. I try to have a balanced and fact-based approach to this subject and to dismantle many of the popular myths. Enjoy!

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About me

My major interest always have been extinct animals, from dinosaurs to Pleistocene megafauna and more recent extinctions. Besides that I am interested in evolution, genetics and ecology.
I am also an amateur animal artist, making drawings and models mostly of extinct animals.